Studies will be continued on the transport of peptides, especially endorphins, in choroid plexus by incubation and perfusion methods. The direction of active transport of peptides, from CSF to blood and vice versa will be determined by the perfusion method. We will investigate what factors affect peptide transport, for example, different age of animals. We will also investigate the peptide transport of animals in a diseased state, namely opiate-dependent, sponataneously hypertensive, and diabetic animals.